Scrollable position of a TextSpan within a RichText

问题

I have many TextSpans in my RichText. I would like to scroll in a specific TextSpan, but for knowing the position I need the context. TextSpan is not a widget. So how can I get the TextSpan's position?

I can't use WidgetSpan because my Spans are pieces of the same sentence.

Thanks

来源：https://stackoverflow.com/questions/57907410/scrollable-position-of-a-textspan-within-a-richtext